Rammed earth construction is a construction method that uses compacted earth inside a form to create a structural wall in a building. Each layer is comprised of a six inch layer of earth that is compacted, using a variety of compaction tools, in a repetitive process until the desired wall height is achieved. This method of construction uses local materials to create the desired structures which is beneficial for the local economy as well as saving money on material for the production team. Rammed earth construction is usable in many different environments, with type of structure and design varying based on the materials available. Rammed earth is an effective way for building structures in developing countries where manufacturing costs would present a heavy constraint.
The construction process begins with setting the formwork for the desired structure design. Walls are the most common structures produced using rammed earth, however it can also be used for roofs, floors, furniture, or even garden decoration. Once the formwork is in place, the moist soil is placed in the formwork and compacted to desired compaction. The composition of the soil used on the structure will vary based on location but once removed from the earth is separated to ensure the proper mixture of clay, sand, and gravel are used. In some cases the addition of an additive to help bond the soil particles together is used, but that is dependent on the original soil types. Soil is added to the formwork in six inch layers and then compacted to the desired compaction level. For many years manual compactors such as tampers were used to compact the soil, but more recently the use of pneumatic rammers has become more popular where available. Walls can be made to a varying width depending on the design specifications, however greater depths will mean longer time for the mixture to set. Once all layers are compacted it is common to remove the form work quickly after finishing to help speed up the drying process[1] .
Once completed the walls are structurally strong enough to withstand normal loading as in the case of most domestic homes. In most cases the compressive strength of rammed earth is around 620 psi; although not as strong as concrete, it is certainly strong enough for homes[2] . The earth layers provide a good insulator during both winter and summer, which helps to reduce cost of heating and cooling.
The below video shows a brief time lapse of the construction of a home.
Figure 2: Form work before compacting soil to make wall section
Historical Background
The use of rammed earth construction has been around for centuries including projects such as the Great Wall of China. This method of building was often used in southern Europe and the middle east for construction of homes, city walls, aqueducts, wells, and other common structures. Rammed earth was used for its ease of manufacturing, low skill labor, and accessibility of materials. Common materials included clay, sand, limestone, and gravel. The Great Wall of China was built with a large portion of the foundation being built using rammed earth construction[3] . Some of the oldest rammed earth construction along the wall dates back to over 4,500 years ago. Many ancient structures were made using rammed earth such as the Pyramid of the sun in Mexico that took 2 million tons of rammed earth to make it 70 feet high[4] . Watch towers constructed under Hannibal as well as many Roman buildings used rammed earth. Rammed earth construction has recently become more common due to its efficiency and durability that reduce utility costs.
Historic formwork in Morocco
The Great Wall of China
Pyramid of the Sun in Mexico
Sustainability
Rammed earth construction carries several benefits and advantages over traditional construction processes which will aid in making this process a sustainable option for future construction. In the current industry being able to have a sustainable option for construction is a necessity for the growth of communities and towns. A structure must be economical, attractive, marketable, structurally sound, durable, and growing in an ever changing industrial community.
Material
The use of local materials provides economy for neighboring industry while lowering cost of construction. Local material will change based on the geographic location of the project, but due to the scope and flexibility in most projects, a structurally sound wall or building can be produced in any area. This idea of locally sustainable will help carry rammed earth production as it becomes increasingly difficult to outsource products and materials to remote project sites[5] . Once the composition of the soil at the site location has been determined, the soil can then be adjusted by select fill and additives to help create the most structurally sound structure possible. A major difference in the construction of a rammed earth wall and a concrete wall is the added reinforcement seen in a concrete wall. Because of the soils nature and the techniques used for compaction it is not common to use additional reinforcement such as steel re-bar that is used with concrete construction. A rough cost estimate for a rammed earth wall for a vertical square meter with 30 cm thickness, the cost is around $250 to $300.[6] For a better construction cost estimates contact local suppliers and contractors in the given area.
Durability
In the early years of rammed earth building there were questions about the durability of the structures, thinking that because of the nature of the materials they would fall apart after only a short time. An example of an old structure that uses rammed earth construction is the Great Wall of China which has stood the test of time being almost 2000 years old. In some cases the weather surrounding the construction had an effect on the durability of the materials used, however recent advances have allowed the use of sealants, paints, and added adhesives to help the maintain the structural integrity[7]
Efficiency
Rammed earth structures are more efficient in production and more economical in practice than traditional fired clay brick solutions as well as other masonry solutions. Using rammed earth has been discovered to use about 1/700th the energy required to produce a oven-fired brick structure of the same mass and volume[8] . This proves an incredibly economic solution that fuels future building using rammed earth. The properties of soils will often come in to play in the heating and cooling of rammed earth buildings as in many cases the soil will provide its own insulation, eliminating the need for additional insulation to be installed. The thermal characteristics of the earth make it one of the most environmentally friendly and efficient materials on the market[9] . By eliminating the need for additional insulation, the owners of the structure will save money on operating costs throughout the structure's lifetime. The production of a rammed earth structure is faster than many masonry solutions due to the lack of time needed to set up and cure. Once the soil is compacted the form work can be moved to the next section and continued while the soil continues to dry, leaving a solid wall within a few hours.
Living
There are benefits not only in the construction phases of the building process but also in the ownership of a rammed earth building. Owners get the benefit of a home that is efficient, environmentally friendly, attractive, and provides a unique design desirable by others. In the design phases of construction owners have plenty of options in texture finishes, color schemes, and materials that give each home a personal touch which further helps create a feeling of the house being a home. Because of the environmental benefits of the earth structure, owners have claimed a lower level of allergens and attractiveness that furthers the uniqueness of each building. The design of earth structures often incorporates large open spaces that create a spacious environment while maintaining a cozy feel[10] .
Figure 3: The interior walls show the different layers of soil used while showing the versatility in design.
Figure 4: The exterior of a rammed earth home
Future Construction
Because of the previously discussed efficiency of rammed earth solutions there is a bright future for the use of this construction method. Further research is being conducted to see if this would be a viable solution to be used on large commercial construction, or as the primary construction method for domestic homes. The design of these homes or structures can be made to accommodate nearly any shape, depending on the form work being used. Because of the scope of the uses for rammed earth, there are endless possibilities that can lead to new innovative designs and give owners creative liberty to create unique designs. The economic benefits of this style of building will help to keep local businesses alive and to create jobs for local contracting companies.
Current Construction
Rammed earth construction uses many currently used methods for building like structures. The form work used for rammed earth is similar if not identical to the form work used for pouring of concrete structures. Tamping devices such as hand tamps, vibratory compactors, and pneumatic rams are all examples of tools in use in other construction methods and have been adapted to work with rammed earth construction[11] .
Studies are being performed on rammed earth to see how different moisture contents effect the mechanical characteristics of rammed earth walls.[12] In addition, observations of creep over time are being accounted for to get an idea of how to improve rammed earth structures so that they last over time.
Examples of Current Construction
Figure 5: Layered wall with open slot windows
Figure 6: Rammed earth wall with window
Figure 7: Desert house with rammed earth walls
Figure 8: House with rammed earth wall
For Further Research on Rammed Earth See the Following Websites:
Introduction
Rammed earth construction is a construction method that uses compacted earth inside a form to create a structural wall in a building. Each layer is comprised of a six inch layer of earth that is compacted, using a variety of compaction tools, in a repetitive process until the desired wall height is achieved. This method of construction uses local materials to create the desired structures which is beneficial for the local economy as well as saving money on material for the production team. Rammed earth construction is usable in many different environments, with type of structure and design varying based on the materials available. Rammed earth is an effective way for building structures in developing countries where manufacturing costs would present a heavy constraint.Table of Contents
Construction Process
Once completed the walls are structurally strong enough to withstand normal loading as in the case of most domestic homes. In most cases the compressive strength of rammed earth is around 620 psi; although not as strong as concrete, it is certainly strong enough for homes[2] . The earth layers provide a good insulator during both winter and summer, which helps to reduce cost of heating and cooling.
The below video shows a brief time lapse of the construction of a home.
Historical Background
The use of rammed earth construction has been around for centuries including projects such as the Great Wall of China. This method of building was often used in southern Europe and the middle east for construction of homes, city walls, aqueducts, wells, and other common structures. Rammed earth was used for its ease of manufacturing, low skill labor, and accessibility of materials. Common materials included clay, sand, limestone, and gravel. The Great Wall of China was built with a large portion of the foundation being built using rammed earth construction[3] . Some of the oldest rammed earth construction along the wall dates back to over 4,500 years ago. Many ancient structures were made using rammed earth such as the Pyramid of the sun in Mexico that took 2 million tons of rammed earth to make it 70 feet high[4] . Watch towers constructed under Hannibal as well as many Roman buildings used rammed earth. Rammed earth construction has recently become more common due to its efficiency and durability that reduce utility costs.
Sustainability
Rammed earth construction carries several benefits and advantages over traditional construction processes which will aid in making this process a sustainable option for future construction. In the current industry being able to have a sustainable option for construction is a necessity for the growth of communities and towns. A structure must be economical, attractive, marketable, structurally sound, durable, and growing in an ever changing industrial community.
Material
The use of local materials provides economy for neighboring industry while lowering cost of construction. Local material will change based on the geographic location of the project, but due to the scope and flexibility in most projects, a structurally sound wall or building can be produced in any area. This idea of locally sustainable will help carry rammed earth production as it becomes increasingly difficult to outsource products and materials to remote project sites[5] . Once the composition of the soil at the site location has been determined, the soil can then be adjusted by select fill and additives to help create the most structurally sound structure possible. A major difference in the construction of a rammed earth wall and a concrete wall is the added reinforcement seen in a concrete wall. Because of the soils nature and the techniques used for compaction it is not common to use additional reinforcement such as steel re-bar that is used with concrete construction. A rough cost estimate for a rammed earth wall for a vertical square meter with 30 cm thickness, the cost is around $250 to $300.[6] For a better construction cost estimates contact local suppliers and contractors in the given area.Durability
In the early years of rammed earth building there were questions about the durability of the structures, thinking that because of the nature of the materials they would fall apart after only a short time. An example of an old structure that uses rammed earth construction is the Great Wall of China which has stood the test of time being almost 2000 years old. In some cases the weather surrounding the construction had an effect on the durability of the materials used, however recent advances have allowed the use of sealants, paints, and added adhesives to help the maintain the structural integrity[7]Efficiency
Rammed earth structures are more efficient in production and more economical in practice than traditional fired clay brick solutions as well as other masonry solutions. Using rammed earth has been discovered to use about 1/700th the energy required to produce a oven-fired brick structure of the same mass and volume[8] . This proves an incredibly economic solution that fuels future building using rammed earth. The properties of soils will often come in to play in the heating and cooling of rammed earth buildings as in many cases the soil will provide its own insulation, eliminating the need for additional insulation to be installed. The thermal characteristics of the earth make it one of the most environmentally friendly and efficient materials on the market[9] . By eliminating the need for additional insulation, the owners of the structure will save money on operating costs throughout the structure's lifetime. The production of a rammed earth structure is faster than many masonry solutions due to the lack of time needed to set up and cure. Once the soil is compacted the form work can be moved to the next section and continued while the soil continues to dry, leaving a solid wall within a few hours.Living
There are benefits not only in the construction phases of the building process but also in the ownership of a rammed earth building. Owners get the benefit of a home that is efficient, environmentally friendly, attractive, and provides a unique design desirable by others. In the design phases of construction owners have plenty of options in texture finishes, color schemes, and materials that give each home a personal touch which further helps create a feeling of the house being a home. Because of the environmental benefits of the earth structure, owners have claimed a lower level of allergens and attractiveness that furthers the uniqueness of each building. The design of earth structures often incorporates large open spaces that create a spacious environment while maintaining a cozy feel[10] .Future Construction
Because of the previously discussed efficiency of rammed earth solutions there is a bright future for the use of this construction method. Further research is being conducted to see if this would be a viable solution to be used on large commercial construction, or as the primary construction method for domestic homes. The design of these homes or structures can be made to accommodate nearly any shape, depending on the form work being used. Because of the scope of the uses for rammed earth, there are endless possibilities that can lead to new innovative designs and give owners creative liberty to create unique designs. The economic benefits of this style of building will help to keep local businesses alive and to create jobs for local contracting companies.
Current Construction
Rammed earth construction uses many currently used methods for building like structures. The form work used for rammed earth is similar if not identical to the form work used for pouring of concrete structures. Tamping devices such as hand tamps, vibratory compactors, and pneumatic rams are all examples of tools in use in other construction methods and have been adapted to work with rammed earth construction[11] .
Studies are being performed on rammed earth to see how different moisture contents effect the mechanical characteristics of rammed earth walls.[12] In addition, observations of creep over time are being accounted for to get an idea of how to improve rammed earth structures so that they last over time.
Examples of Current Construction
For Further Research on Rammed Earth See the Following Websites:
http://www.rammedearthconstructions.com.au/
http://earthstructures.com.au/
http://www.murchisonrammedearth.com.au/
http://www.ramtec.com.au/
http://www.uniqueearth.com.au/
http://www.rammedearthworks.com/
http://sirewall.com/
<http://www.sciencedirect.com/science/article/pii/S0950061813012245>
<http://builditbackgreen.org/bushfires/interactive-green-building-guide/building-materials/rammed-earth.aspx>
December 2, 2015